Selection Procedures - Trane CGAD020C Manual

Liquid chiller capacity tables 03 and 04, on
pages 11 and 12 show the most frequent
leaving water temperatures. The table
reflects a temperature drop of 5,5 ºC (10ºF)
through the evaporator. For low tempera-
ture selections, refer to figures 04 and 05
for Adjustment Factors of Ethylene and
Propylene Glycol.
To select a CGAD Air-Cooled Liquid Chiller
Trane, the following information is
required:
1
Thermal project load of project in tons of
cooling.
2
Chilled water temperature project drop.
3
Leaving chilled water project temperature.
4
Project ambient temperature and refriger-
ant type.
The evaporator flow is determined
through the following formulas:
Tons X 24
GPM =
Temperature drop (°F)
kW (Capacity) X 0,239
L/s =
Temperature drop (°C)
NOTE 1:
The flow should be within the limits
specified in table 01, General Data
(page 05).
Note:
The selection above is an example for manual equipment selection. Please note that a more accurate data check is required for a correct selection.
6
Selection
Procedures
Selection example:
Data:
System load required= 70 Tons.
Leaving chilled water temp. = 7ºC
Chilled water temperature drop = 5,5ºC
(10°F)
Project ambient temperature = 35ºC
1
Calculate the required chilled water flow
using the formula below:
GPM = 70 Tons x 24 = 168 GPM
10ºF
2
Using table 03 (Performance Data - R-22), a
CGAD 080 unit at these conditions will
output 76,2 Tons with a compressor
consumption of 81,1 kW.
3
Determine the evaporator pressure drop
using the flow and the evaporator water
pressure drop curves, figure 05.
Introducing the curve at 168 GPM, the
pressure drop for an evaporator with the
nominal value of 80 Tons is 9 ft, or 2,74 m.
4
For selection of low temperature units, or
applications in which the altitude is
significantly above sea level, or the
temperature drop is different from 5,5 ºC,
contact a local Trane engineer for further
information.
For example:
Corrected capacity = Capacity (not
adjusted) x Glycol Capacity Adjustment
Factor
Corrected Flow = Flow (not adjusted) x
Glycol Flow Rate Adjustment Factor
5
The final unit selection is: CGAD 080B
Refrigerant Type: R-22
Cooling capacity =76,2 Tons.
Entering temperatures = 12,5 °C
Leaving chilled water temperature = 7ºC
Chilled water flow =168 GPM
Evaporator pressure drop =2,74 m
Compressor consumption = 81,1 kW
NOTE 2:
Minimum leaving chilled water tempera-
ture setpoint
The minimum leaving chilled water
temperature setpoint is 4ºC. For applica-
tions where a lower setpoint is required, a
glycol solution must be used. Contact the
local Trane engineer for further information.
CG-PRC002A-EN